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Discussion Starter #1 (Edited)
Cost for either amp: $800 + shipping ( +$50 for original vinyl cover; only one available).

Would consider trades for a few high-gain amps, including Ceriatone, Fortin Sigil, Victory Kraken, Revv G20.


Completely overhauled YBA-1 amps from the mid 70s. Serviced and modified.

** Service and updating for each amp **
  • New tubes (EL34 or 5881)
  • New 12000-hr caps loaded on my own custom PCBs
  • New grounding scheme and some power supply tweaks to make the amp WAY quieter, even with way more gain.
  • New 3-prong power cord (with ground switch and death cap removed) for safety.
  • Bias trim pot added for quick bias adjustment.
  • Original fragile wires replaced for reliability (essentially, all original wires will break if lightly stressed).
** tone mods, Amp 1 **
Similar to single-channel Friedman Smallbox, with Low- and High-sensitivity inputs for 2 or 3 gain stages, respectively. Depth knob on rear panel. Mini switches for bright/bite (three position), gain structure, Fat, and 'era' (low/high gain for high-sensitivity input).

** tone mods, Amp 2 **
Single-channel SLO-based mod with low- and high-sensitivity inputs for 3 or 4 gain stages, respectively. A solid-state source follower was built on a custom PCB to drive tone stack (since I didn't want to drill the chassis for another 12AX7). SLO preamp values tweaked a bit, similar to what Baron55 recommended on the SloClone forum. Depth knob and Fat/tight switch added on rear panel.

Amp #1:
330136

330138

330139

330141


Amp #2:
330725

330726

330727

330730

330731


cover:
330732
 

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Discussion Starter #7
Sorry for the confusion, folks. The cost is $900 for either (individual) amp, not for the pair. I've updated my post(s) to clarify.
 

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Discussion Starter #8
price drop $800 + shipping for either.
 

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Discussion Starter #9
Sale of amp #1 (Friedman-type) pending...
 

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Discussion Starter #10
Amp #1 is SOLD!
Amp #2 is available, but since I've got the urge to mod, I'm going to reconfigure the preamp to Roccaforte HG100 specs (at least for the time being).
 

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Amp #1 is SOLD!
Amp #2 is available, but since I've got the urge to mod, I'm going to reconfigure the preamp to Roccaforte HG100 specs (at least for the time being).

How does the HG100 sound differ from the SLO specs? Do you have to get rid of that nifty gain stage PCB you designed for this mod?
 

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Discussion Starter #12 (Edited)
How does the HG100 sound differ from the SLO specs? Do you have to get rid of that nifty gain stage PCB you designed for this mod?
I did pull out the PCB after changing the input gain stage to what I want for HG100. I might add it back in to my HG preamp, tho.

The HG pre was designed by Kevin O'Connor of London Power and appeared in one of his TUT books. It has 4 gain stages and a plate-driven tone stack (which KOC prefers). The HG100 used linear pots for gain and volume; mine will have audio-taper pots for more gradual increase in gain and volume. And I'll add in a low-sensitivity input and possibly a bypass for the third gain stage. The low-sensitivity input of my SLO-inspired preamp was a bit dark; the HG will be better.
 
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